The priority claim is of Pat. No. PCT/GB98/00713, filing date Mar. 5, 1998, Priority date Mar. 5, 1997
This invention relates to a hinge mechanism for a limb protector for the joint of a human limb, that is a knee or elbow protector. Therefore it can have related application as a knee or elbow brace.
Injuries to the limbs and their joints occur for several reasons, including participation in contact sports such as American football ice hockey, in individual sports such as skiing or motorcycle racing or indeed any active sport. In addition injuries to limbs and their joints occur in active occupations such as armed forces, or in any type of accident.
After an injury occurs, it is often desirable to either slightly restrict the movement of the limb or the joint, for example by elastic support, or severely restrict movement of the limb or joint by ridged splits, or ridged braces that restrict the degree of movement of the limb or joint, for example by hinged knee or elbow braces, (de-rotational braces).
Such braces which are available to prevent twisting of a knee or elbow can be worn during activities such as skiing and can have preventative as well as protective effect. Such hinged braces are by their very nature restrictive of movement and permit only forward bending of the knee or elbow. Other braces are available for sports such as American football which protects the knee against side impact or frontal impact but also restrict movement (prophylactic or preventative braces). Dynamic braces are also available with eccentrically placed hinges to provide protection to torn ligaments. The present invention relates to rigid hinged braces.
WO 94/18916 discloses a variety of hinged braces to be worn for the protection or support of a damaged or potentially damageable joint. The braces disclosed have, when applied to a knee joint, respective upper and lower rigid supports which engage the leg above and below the knee and which are hinged one to the other to allow bending of the joint.
Because of the way the joint of the human knee is physically constructed the bending of a joint can occur around any point within a given area covering that joint when that joint is viewed from the side, or in a direction substantially parallel to the axis of rotation of the exact point about which the joint rotates is dependent upon the the limb either side of the joint, or the amount by which the limb, and hence the joint has already been bent. When for example the joint being rotated is the knee, the points about which rotation may occur may be either side of the cartilage that separates the tibia and fibula bones on the one side, and the femur on the other side of the knee joint or on both sides of the cartilage. Accordingly, to hinge the upper and lower supports together about a simple pivot is unsatisfactory. Instead, in preferred constructions as shown in FIGS. 5 and 16 of WO 94/18916, each is pivoted to an intermediate member and the two intermediate members are pivoted to one another. This allows the axis of rotation to vary relative to the joints, e.g. When moving from standing vertically to bending one""s knees. The assembly shown in WO94/18916 are cumbersome and complex to assemble, and require the manufacture of a plurality of telescopic shells which must slide over one another easily, but which must be sufficiently rigid and impact resistant (as such braces are often worn during contact sport play to enable play to occur but reducing the risk of further injury to a recovering limb) to ensure that such movement can be maintained without jamming. These criteria are not easy to meet.
I have now found that a much more effective and robust hinging mechanism can be provided which maintains the flexibility of movement provided by the constructions shown in WO 94/18916, but which does not incur its disadvantages. In particular, it may enable easy assembly and disassembly and is very resistant to mechanical damage.
The development of this invention was funded by the United Kingdom Grant: Supports for Products Under Research grant, this grant was known as the SPUR grant.
According to the present invention there is provided a hinge mechanism for a limb protector including first and second supports each adapted to engage a part of a limb in either side of an articulated joint, the hinge mechanism being pivotally connected to both supports, and wherein the hinge mechanism comprises a base plate, an arm pivotally rotatable against the plate about an axis substantially perpendicular thereto and located to one end of the arm and means (by way of connecting screws) for connecting the support members pivotally to the other end of the arm and to the plate, all of these three axes of rotation of the pivotal connections being substantially parallel, and wherein associated with each of the three pivotal connections are means for restricting the relative degree of rotation of the respective two members to a defined amount.
Preferably, the arm is mounted rotationally on a circular boss on the plate and the plate has stop means formed thereon restricting the angular rotation of the arm, e.g. to a maximum of 60 degrees. Preferably, the angular rotation of each support member relative to the end of the arm or the base plate respectively is restricted by the passage of a stud or post along an arcuate slot centred on the pivot axis.
The post is conveniently on the base or arm and the arcuate slot in the support member. The extent of the arcuate slot may vary, but is commonly in the range of 50 degrees to 110 degrees.
By hinging of the supports together using a hinge mechanism according to the present invention, with all three pivots having a restricted degree of rotation, the degree of rotation of each of the first, second and third pivotal connections may be set to predetermine the maximum translational and rotational movement between the bones of the joint around which the brace is to be fixed. This may be achieved by providing slots of lengths corresponding to the maximum likely desired degree of pivotal movement, e.g. 60 and 90 degrees and then limiting the degree of rotation of either or both slots by inserting into the arcuate slot spacers or other means of preventing rotation, so that the relevant studs or posts may move only along a portion of that slot.
The degree of rotation available to the arm may be limited by locating the arm in a recessed portion of the plate which is bounded by radial walls e.g. inclined at 60 degree to one another. To limit the degree of rotation further spacers or other means of preventing rotation may be fixed within the recess. In place of a recess with walls, the amount of rotation of the arm may be defined by studs mounted on the plate. The hinge mechanism of the present invention may be made of any suitable material, preferably aluminium alloy, though, if desired, suitable engineering plastics materials may be used. The support members are conventionally made of rigid material. In order to avoid over stressing such materials where they are connected to the hinge mechanism, reinforcements, e.g. of metal, may be installed. In particular, it is found useful to reinforce the edges of the arcuate slots with a metal plate or liner.
In use, each limb protector or brace would have a hinge mechanism according to the present invention on either side of the joint around which the brace was placed.
The hinge of the present invention may be employed on all currently known types of kneebrace once suitable modification has been made to those knee braces. In particular, the present invention is of value applied to braces as described in WO 94/18916, with the arrangement as described above replacing the front plates of the hinged brace described therein.